The present invention relates to an improved weft winder of a weaving machine for winding and supplying a weft to warp in the weaving process.
The weft winder for a weaving machine generally has a structure as shown in FIG. 6. The weft winder comprises an outer frame member 1 constituted by a hollow cylinder made of aluminum alloys, etc. and having an inner conical surface 2 at one end, a rotor 3 having a pipe 4 projecting from one end thereof for guiding a weft 5 and disposed in the outer frame member 1 such that it is concentrically rotatable, and an inner frame member 6 made of aluminum alloys etc. and rotatably supported by the rotor 3 via bearings 7 concentrically with the rotor 3. The inner frame member 6 is provided at a free end (inner end) thereof with an outer conical surface 8 facing the inner conical surface 2 of the outer frame member 1 via a gap G therebetween, and the pipe 4 of the rotor 3 extends through the gap G. The inner frame member 6 has a weft-winding portion 9 for winding the weft 5 supplied from the pipe 4 at the outer end.
FIG. 7 shows the details of a portion A in FIG. 6. In FIG. 7, the same members are assigned the same reference numerals as in FIG. 6. The inner conical surface 2 of the outer frame member 1 and the outer conical surface 8 of the inner frame member 6 are each provided with a plurality of magnet members 10 each constituted by a plate-shaped magnet 10a a and a yoke 10b. Each magnet 10a is magnetized in a thickness direction, and a plurality of magnets 10a are arranged in a circumferential direction such that N poles and S poles are arranged alternately. Also, the magnets 10a on the inner conical surface 2 and the magnets 10a on the outer conical surface 8 are opposite each other with their different magnetic poles facing each other. Incidentally, the plate-shaped magnet 10a is preferably in the shape of a disc, and the yoke 10b is preferably constituted by an iron plate formed substantially in the shape of a bowl. The magnet 10a is fixed to the yoke 10b, which is in turn fixed to each of recesses formed in the inner conical surface 2 and the outer conical surface 8 via a bolt 11.
With the above construction, the rotor 3 can be rotated with a gap G between the inner conical surface 2 of the outer frame member 1 and the outer conical surface 8 of the inner frame member 6 kept constant due to a magnetic attraction of the magnet members 10, 10. Thus, the weft 5 guided through the pipe 4 can be wound around the weft-winding portion 9 of the inner frame member 6.
In the weft winder for a weaving machine having the above construction, however, there should be a large number of magnet members 10 in order to keep the inner frame member 6 stationary relative to the outer frame member 1 with a gap G between the inner conical surface 2 and the outer conical surface 8 kept at a constant distance. For instance, with the magnet members 10 each having a diameter of 21 mm, 24 magnet members are arranged. This leads to a close distance between the adjacent magnet members 10, 10 on the inner conical surface 2 and the outer conical surface 8, making it likely to have a short circuit of magnetic flux between the adjacent magnet members 10, 10. This in turn leads to the reduction of a magnetic attraction between the opposing magnet members 10 and 10.
For the purpose of increasing a magnetic attraction, it may be considered to reduce the gap G between the inner conical surface 2 and the outer conical surface 8. However, this is impossible because the pipe 4 usually rotating at a high speed of 2,000-2,500 rpm is vibrated to some extent. On the other hand, since part of the yoke 10b extends outside the magnet 10a, a short-circuiting of the magnetic flux would also take place in the extended yoke portions. Therefore, a large number of strong magnet 10a should be used, which would lead to a large weight and high cost of the weft winder.
Japanese Utility Model Laid-Open No. 61-142887 discloses a weft winder for a fluid jet-type weaving machine which comprises magnets contained in magnetic capsules which are fixed to inner surfaces of U-shaped magnetic yokes in order to maximize the magnetic attraction of magnets. However, this magnet members has a complicated structure and is not necessarily sufficient in terms of magnetic attraction between the opposing magnet members.
To solve the above problem, an improved weft winder for a weaving machine was previously proposed by Japanese Utility Model Laid-Open No. 1-87183. This weft winder has a structure in which each magnet is lined with a yoke such as an iron plate and fixed to each of the inner conical surface of the outer frame member and the outer conical surface of the inner frame member by bolts. By this structure, this weft winder shows sufficient magnetic attraction between the opposing magnet members with smaller numbers of magnet members than those of the conventional ones. However, further improvement is desired to meet increasingly higher demands of performance and cost.